Various means have been used in the prior art which are responsive to the normal acceleration environment of a projectile flight in order to ensure that the projectile has been properly launched from the gun as against the possible inadvertent exposure to an environment which merely simulates launch conditions. Prior art devices which seek to achieve safety of a munition by preventing premature arming without the use of electrical components, generally use mechanical clock type mechanisms or a complex system involving levers and gears. The aforementioned prior art devices are not only expensive to manufacture because of their complexity, but also require special care in storage. In prior art mechanical fuzes it is important, for proper subsequent operation of the device, to control the storage environment in order to prevent corrosion damage to delicately meshed gear train mechanisms and low friction pivoted levers.